Direct outlet toroidal plasma source

ABSTRACT

An apparatus for supplying plasma products includes a plasma generation block that defines a toroidal plasma cavity therein. The plasma cavity is substantially symmetric about a toroidal axis, and the toroidal axis defines a first and second axial side of the plasma generation block. A magnetic element at least partially surrounds the plasma generation block at one azimuthal location with respect to the toroidal axis, such that a magnetic flux within the magnetic element induces a corresponding electric field into the plasma cavity to generate a plasma from one or more source gases, the plasma forming plasma products. The plasma generation block supplies the plasma products through a plurality of output apertures defined by the plasma generation block on the first axial side.

TECHNICAL FIELD

The present disclosure applies broadly to the field of plasma processingequipment. More specifically, systems and methods for providingspatially uniform plasma products are disclosed.

BACKGROUND

Semiconductor processing often utilizes plasma processing to etch, cleanor deposit material on semiconductor wafers. All such processes areadvantageously highly uniform over the entire surface of a processedwafer. Wafer sizes have increased while feature sizes have decreased,significantly over the years, so that more integrated circuits can beharvested per wafer processed. Typical wafer diameters increased fromabout 2 or 3 inches in the 1970s to 12 inches or more in the 2010s. Overthe same time frame, typical minimum feature sizes of commercialintegrated circuits decreased from about 5 microns to about 0.015microns. Processing smaller features while wafers grow larger requiressignificant improvements in processing uniformity. Plasma processing ofworkpieces other than wafers may also benefit from improved processinguniformity.

SUMMARY

In an embodiment, an apparatus for supplying plasma products includes aplasma generation block that defines a toroidal plasma cavity therein.The plasma cavity is substantially symmetric about a toroidal axis, andthe toroidal axis defines a first and second axial side of the plasmageneration block. A magnetic element at least partially surrounds theplasma generation block at one azimuthal location with respect to thetoroidal axis, such that a magnetic flux within the magnetic elementinduces a corresponding electric field into the plasma cavity togenerate a plasma from one or more source gases, the plasma formingplasma products. The plasma generation block supplies the plasmaproducts through a plurality of output apertures defined by the plasmageneration block on the first axial side.

In an embodiment, an apparatus for supplying plasma products includes aplasma generation vessel that defines a plasma cavity. The plasma cavityis substantially symmetric about a toroidal axis. The plasma generationvessel includes (1) a plasma generation block that bounds the plasmacavity on radially inward, radially outward, and second axial sidesthereof, and defines one or more apertures for introducing one or moresource gases into the plasma cavity; and (2) a planar plate disposed ona first axial side of the plasma cavity, the planar plate defining aplurality of apertures therethrough that are azimuthally distributedabout the plasma cavity. Radially inward and radially outward edges ofthe plasma generation block abut the planar plate to form the plasmageneration vessel, substantially enclosing the plasma cavity. Theapparatus further includes first and second induction coils, a powersupply for providing currents within the first and second inductioncoils, and first and second magnetic elements extending at leastpartially about the plasma generation block and disposed proximate thefirst and second induction coils respectively, so that the currentsinduce magnetic fluxes within the magnetic elements, and the magneticfluxes within the magnetic elements produce azimuthal electric fieldswithin the plasma cavity to form a plasma from the one or more sourcegases, forming plasma products. The apertures through the planar plateprovide fluid communication for the plasma products to an adjacentregion for use in plasma processing.

In an embodiment, a method for providing plasma products includesintroducing a source gas stream into a plasma generation block thatdefines a toroidal plasma cavity therein. The plasma cavity issubstantially symmetric about a toroidal axis. The plasma generationblock defines a plurality of output apertures only on a first axial sidethereof relative to the toroidal axis. The output apertures aresubstantially azimuthally distributed about the plasma generation block.The method also includes inducing an electric field into the plasmacavity to generate a plasma from the source gas stream, the plasmaforming the plasma products, and passing the plasma products through theplurality of output apertures defined by the plasma generation block.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates major elements of a plasma processingsystem, according to an embodiment.

FIG. 2 schematically illustrates selected elements of a direct outlettoroidal plasma source, according to an embodiment.

FIG. 3 schematically illustrates selected elements of a direct outlettoroidal plasma source, according to an embodiment.

FIG. 4 schematically illustrates selected elements of a direct outlettoroidal plasma source, according to an embodiment.

FIG. 5 schematically illustrates selected elements of a direct outlettoroidal plasma source, according to an embodiment.

FIG. 6 is a schematic cutaway view of the direct outlet toroidal plasmasource of FIG. 5, taken at broken line 6-6.

FIG. 7 is a schematic cutaway view of the direct outlet toroidal plasmasource of FIG. 5, taken at broken line 7-7.

FIG. 8 schematically illustrates a direct outlet toroidal plasma sourcehaving a plasma cavity that is defined by disposing a plasma blockadjacent a plate, according to an embodiment.

FIG. 9 schematically illustrates another direct outlet toroidal plasmasource having a plasma cavity that is defined by disposing a plasmablock adjacent a plate, according to an embodiment.

FIG. 10 schematically illustrates a direct outlet toroidal plasmasource, showing an inlet gas manifold that supplies source gases to aplasma cavity therein, according to an embodiment.

FIG. 11 is a schematic cutaway view along line 11-11 of FIG. 10.

FIG. 12 schematically illustrates a plasma block of a direct outlettoroidal plasma source with an inline gas injection port for introducingsource gases, according to an embodiment.

FIG. 13 schematically illustrates a plasma block of a direct outlettoroidal plasma source with a plurality of inline gas injection portsfor introducing source gases, according to an embodiment.

FIG. 14 schematically illustrates a plasma block of a direct outlettoroidal plasma source, showing how outlet apertures may be defined at aplurality of angles with respect to a surface normal of a plate thatforms one axial side thereof, according to an embodiment.

FIG. 15A is a schematic bottom view illustrating a direct outlettoroidal plasma sources in which four outlet apertures are defined,according to an embodiment.

FIG. 15B is a schematic bottom view illustrating a direct outlettoroidal plasma sources in which over sixty outlet apertures aredefined, according to an embodiment.

FIG. 16 schematically illustrates, in a cross-sectional view, a plasmawafer processing system that includes two direct outlet toroidal plasmasources, according to an embodiment.

FIG. 17A schematically illustrates an upward facing, schematic plan viewof a top surface of the plasma processing system of FIG. 16, withfeatures of a bottom plate of the two direct toroidal plasma sourcesvisible.

FIG. 17B schematically illustrates an upward facing, schematic plan viewof a diffuser plate of the plasma processing system of FIG. 16.

FIG. 18 schematically illustrates, in a cross-sectional view, a plasmawafer processing system that includes two direct outlet toroidal plasmasources, according to an embodiment.

DETAILED DESCRIPTION

The present disclosure may be understood by reference to the followingdetailed description taken in conjunction with the drawings describedbelow, wherein like reference numerals are used throughout the severaldrawings to refer to similar components. It is noted that, for purposesof illustrative clarity, certain elements in the drawings may not bedrawn to scale. Specific instances of an item may be referred to by useof a numeral in parentheses (e.g., plasma blocks 210(1), 210(2), etc.)while numerals without parentheses refer to any such item (e.g., plasmablocks 210). In instances where multiple instances of an item are shown,only some of the instances may be labeled, for clarity of illustration.

FIG. 1 schematically illustrates major elements of a plasma processingsystem 100, according to an embodiment. System 100 is depicted as asingle wafer, semiconductor wafer plasma processing system, but it willbe apparent to one skilled in the art that the techniques and principlesherein are applicable to plasma generation systems of any type (e.g.,systems that do not necessarily process wafers or semiconductors). Itshould also be understood that FIG. 1 is a simplified diagramillustrating only selected, major elements of system 100; an actualprocessing system will accordingly look different and likely containadditional elements as compared with system 100.

Processing system 100 includes a housing 110 for a wafer interface 115,a user interface 120, a plasma processing unit 130, a controller 140 andone or more power supplies 150. Processing system 100 is supported byvarious utilities that may include gas(es) 155, electrical power 170,vacuum 160 and optionally others. Internal plumbing and electricalconnections within processing system 100 are not shown, for clarity ofillustration.

Processing system 100 is illustrated as a so-called indirect, or remote,plasma processing system that generates a plasma in a first location anddirects the plasma and/or plasma products (e.g., ions, molecularfragments, free radicals, energized species and the like) to a secondlocation where processing occurs. Thus, in FIG. 1, plasma processingunit 130 includes a remote plasma source 132 that supplies plasma and/orplasma products for a process chamber 134. Process chamber 134 includesone or more wafer pedestals 135, upon which wafer interface 115 places aworkpiece 50 for processing. Workpiece 50 is, for example, asemiconductor wafer, but could any other type of workpiece to besubjected to plasma processing. In operation, gas(es) 155 are introducedinto plasma source 132 and a radio frequency generator (RF Gen) 165supplies power to ignite a plasma within plasma source 132. Plasmaand/or plasma products pass from plasma source 132 to process chamber134, where workpiece 50 is processed. Typical present day systems may,for example, transfer the plasma and/or plasma products through a nozzle133 and/or a diffuser plate 137 in an attempt to spread and apply themuniformly. An actual plasma system may provide many other optionalfeatures or subsystems through which plasma, plasma products and/orcarrier or additional processing gases flow and/or mix between plasmasource 132 and process chamber 134.

The elements illustrated as part of system 100 are listed by way ofexample and are not exhaustive. Many other possible elements, such as:pressure and/or flow controllers; gas or plasma manifolds ordistribution apparatus; ion suppression plates; electrodes, magneticcores and/or other electromagnetic apparatus; mechanical, pressure,temperature, chemical, optical and/or electronic sensors; wafer or otherworkpiece handling mechanisms; viewing and/or other access ports; andthe like may also be included, but are not shown for clarity ofillustration. Various control schemes affecting conditions in processchamber 134 are possible. For example, a pressure may be maintained bymonitoring the pressure in process chamber 134 and adjusting all gasflows upwards or downwards until the measured pressure is within sometolerance of a desired pressure. Temperatures can be controlled byadding heaters and temperature sensors. Optical sensors may detectemission peaks of plasmas as-generated and/or as they interact withworkpieces.

Internal connections and cooperation of the elements illustrated withinsystem 100 are also not shown for clarity of illustration. In additionto RF generator 165 and gases 155, other representative utilities suchas vacuum 160 and/or general purpose electrical power 170 may connectwith system 100. Like the elements illustrated in system 100, theutilities illustrated as connected with system 100 are intended asillustrative rather than exhaustive; other types of utilities such asheating or cooling fluids, pressurized air, network capabilities, wastedisposal systems and the like may also be connected with system 100, butare not shown for clarity of illustration. Similarly, while the abovedescription mentions that plasma is ignited within remote plasma source132, the principles discussed below are equally applicable to so-called“direct” plasma systems that create a plasma in a the actual location ofworkpiece processing.

Although an indirect plasma processing system is illustrated in FIG. 1and elsewhere in this disclosure, it should be clear to one skilled inthe art that the techniques, apparatus and methods disclosed herein mayalso be applicable to direct plasma processing systems—e.g., where aplasma is ignited at the location of the workpiece(s). Similarly, inembodiments, the components of processing system 100 may be reorganized,redistributed and/or duplicated, for example: (1) to provide a singleprocessing system with multiple process chambers; (2) to providemultiple remote plasma sources for a single process chamber; (3) toprovide multiple workpiece fixtures (e.g., wafer pedestals 135) within asingle process chamber; (4) to utilize a single remote plasma source tosupply plasma products to multiple process chambers; and/or (5) toprovide plasma and gas sources in serial/parallel combinations such thatvarious source gases may be activated (e.g., exist at least temporarilyas part of a plasma) zero, one, two or more times, and mixed with othersource gases before or after they enter a process chamber, and the like.Gases that have not been part of a plasma are sometimes referred to as“un-activated” gases herein.

FIG. 2 schematically illustrates selected elements of a direct outlettoroidal plasma source 200, according to an embodiment. Plasma source200 is an example of remote plasma source 132, FIG. 1. A usefulcoordinate system that will be used herein for describing the featuresshown in FIG. 2 and elsewhere defines axial positions as being along atoroidal axis 1, radial directions 2 as denoting distance from toroidalaxis 1, and azimuthal directions 3 as denoting rotational directionabout toroidal axis 1. Plasma sources disclosed herein will beconsidered to define a toroidal axis that passes through a centroid ofthe plasma source (not necessarily through a physical feature of theplasma source), with a plasma generation cavity of the plasma sourcebeing generally toroidal, radially symmetric with respect to thetoroidal axis, and extending about the toroidal axis in a plane that isperpendicular to the toroidal axis. A major circumference 21 of atoroidal element is defined as extending azimuthally about the toroidalaxis at its outer bound, e.g., as shown for plasma block 210(1) below;major circumference 21 is not shown extending all the way around plasmablock 210(1) in FIG. 2, for clarity of illustration. A minorcircumference extends about an element such as plasma block 210(1) at asingle azimuthal location relative to the toroidal axis 1, e.g., asshown as minor circumference 22, FIG. 2.

Plasma source 200 includes plasma block 210(1), a magnetic element220(1) and an induction coil 230. Magnetic element 220(1) extends atleast partially about plasma block 210(1), and induction coil 230 windsat least partially about magnetic element 220(1). Although magneticelement 220(1) is shown in a toroidal shape, it is not necessary thatmagnetic elements 220 be toroidal, have a round cross section or extendcompletely about a plasma block 210.

Plasma block 210(1) may be evacuated, and plasma source gases may beintroduced into plasma block 210(1). With the plasma source gases withinplasma block 210(1), current is passed through induction coil 230,inducing magnetic flux within magnetic element 220(1), which in turninduces an electric current within plasma block 210(1), igniting aplasma.

Plasma source 200 can thus be seen to resemble a transformer in which aprimary current flows through induction coil 230 and a secondary currentflows within plasma block 210(1). Advantageously, plasma source 200confines the secondary current within the gases and/or plasma ignitedwithin plasma block 210(1), thus, advantageously, plasma block 210(1) isnot formed of a conductor that defines a complete azimuthal circuit. Incertain embodiments, plasma block 210(1) is fabricated of a dielectricmaterial, however, as discussed below, aluminum is often a convenientmaterial from which to make at least portions of plasma block 210(1).When plasma block 210(1) is made from aluminum or another substantiallyconductive material, external fields can be coupled into plasma block210(1) and the azimuthal circuit path can be interrupted by includingone or more dielectric breaks 240 that extend about the minorcircumference of plasma block 210(1).

Plasma block 210(1) defines a plurality of output apertures, at multipleazimuthal locations, but on a single axial side thereof, through whichplasma products are distributed, for use in plasma processing. Forexample, in FIG. 2, the output apertures are not visible, but connectwith outlets 250 to distribute the plasma products in the direction ofthe arrows shown. By providing output apertures at multiple azimuthallocations about one axial side of plasma block 210(1), plasma source 200advantageously provides a circular distribution of outlets 250 such thatplasma products provided therein are equally distant from the plasmathat generates them. This allows direct coupling of a circular patternof plasma products to a process chamber, such that the plasma productsreach the process chamber in a circular and spatially broad patternwhile all points of the pattern are at a substantially equal distancefrom the plasma.

One advantage of the direct outlet toroidal plasma source embodimentsherein lies in providing plasma products across a wide and circularlysymmetric pattern in which all points are substantially equidistant fromthe plasma. This minimizes differences in recombination effects and walleffects that would otherwise affect process results at differinglocations. While typical inductive plasma systems may generate plasmaproducts utilizing a toroidal plasma chamber, such systems typicallydistribute the plasma products through a single port or nozzle thatprovides differing distances from the plasma to various locations on theworkpiece.

Another advantage of the embodiments herein lies in the ability togenerate plasmas at relatively high pressures without excessivesputtering damage to internal surfaces due to ions being accelerated byhigh electric fields. Embodiments herein can be operated, for example inpressure regimes of 0.5 Torr or less to 100 Torr or more. Other types ofinductively coupled plasma sources often expose plasma blocks to highelectric fields, such fields typically arising from induction coils thatare positioned near to the plasma block. Ions in the plasma thatexperience such fields are accelerated in the direction of the fields,often striking the internal plasma block walls and sputtering thematerial thereof. Sputtering damage results in reduced equipmentlifetime and/or excessive maintenance requirements, incurring labor andmaterial costs, and tool downtime. In contrast, the designs hereinminimize exposure of plasma blocks to electric fields except along thedirection of the toroidal plasma cavity, such that magnetic flux steeredby magnetic elements generates secondary current within the plasmaitself without introducing electric fields that would cause sputteringof the plasma block surfaces. This, in turn, enables at least someembodiments herein to use plasma blocks made primarily of aluminum withuntreated surfaces, as opposed to more expensive materials, or aluminumwith specially treated surfaces. Treated surfaces remain an option.

Magnetic elements 220 herein are typically formed of ferrite. Inductioncoils 230 are typically formed of copper, optionally plated with silverfor decreased outer skin electrical resistivity. Both magnetic elements220 and induction coils 230, and certain regions or parts of plasmablocks 210, may include channels for cooling gases or liquids, asdiscussed further herein, to remove heat generated by electrical andmagnetic losses during operation. As noted above, plasma blocks 210 maybe fabricated of aluminum with untreated surfaces, or with surfacetreatments such as anodization, or alumina, aluminum nitride or yttriacoatings. Other material choices are also possible and may be made byconsidering cost, machinability, electrical conductivity, thermalexpansion, heat dissipation characteristics, and compatibility withintended gases and plasma products.

FIG. 3 schematically illustrates selected elements of a direct outlettoroidal plasma source 300. Plasma source 300 shares many of the sameelements with plasma source 200, FIG. 2, but includes a plasma block210(2), two magnetic elements 220(1) with respective induction coils230. The toroidal axis 1, radial direction 2 and azimuthal direction 3are shown again in FIG. 3 for reference. For symmetric and efficientplasma generation, magnetic elements 220(1) are located azimuthallyopposite one another about plasma block 210(2). Also, plasma block210(2) of plasma source 300 includes four dielectric breaks 240; twodielectric breaks 240 are located near magnetic elements 220(1) whilethe other two are located at 90 degree intervals about the circumferenceof plasma block 210(2) from magnetic elements 220(1).

FIG. 4 schematically illustrates selected elements of a direct outlettoroidal plasma source 400. Plasma source 400 shares many of the sameelements with plasma source 200 and 300, but includes two magneticelements 220(2) that are U- or horseshoe-shaped, instead of toroidal.Use of U- or horseshoe-shaped magnetic elements helps facilitate certainconstructions of direct outlet toroidal plasma sources, as furtherdescribed below.

FIG. 5 schematically illustrates selected elements of a direct outlettoroidal plasma source 500. Toroidal axis 1, radial direction 2 andazimuthal direction 3 are not shown again in FIG. 5, for clarity ofillustration, but remain as defined in FIG. 2. Plasma source 500 sharesmany of the same elements with plasma source 200, 300 and 400. Plasmablock 210(3) includes metal sections 245 with dielectric breaks 240 (twoof which are hidden by magnetic elements 220(3) in the view of FIG. 5.Plasma block 210(3) is flattened on an axial side 211(1) (labeled, buthidden in the view of FIG. 5). Plasma block 210(3) defines inletapertures 260 in sections 245. Plasma block 210(3) also defines outletapertures 270 on axial side 211(2), as shown. The locations and numbersof inlet apertures 260 and outlet apertures 270 shown in FIG. 5 aremerely illustrative; not all instances of such apertures are shown orlabeled, for clarity of illustration. In practice, inlet apertures 260may be located to provide uniform source gas introduction into plasmablock 210(3), but may otherwise be arranged for convenient integrationwith other components of plasma source 500. Outlet apertures 270 aretypically more numerous than shown in FIG. 5, are arranged to provideuniform plasma product distribution to an adjacent process chamber, andmay be defined either in sections 245 or dielectric breaks 240 (seeFIGS. 6 and 7). Broken lines 6-6 and 7-7 denote planes at which thecutaway views shown in FIGS. 6 and 7, respectively, are taken.

FIGS. 6 and 7 are schematic cutaway views of direct outlet toroidalplasma source 500 taken at broken lines 6-6 and 7-7, respectively, ofFIG. 5. FIG. 6 shows the cutaway taken through one of dielectric breaks240 (hidden beneath magnetic elements 220(3) in the view of FIG. 5). Thetoroidal axis 1 and radial direction 2 are shown again in FIGS. 6 and 7for reference; azimuthal direction arcs in or out of the planes of FIGS.6 and 7, changing sign from left to right of toroidal axis 1. Someoutlet apertures 270 are defined by dielectric break 240 on axial side211(2) of plasma block 210(3), as shown. A plasma cavity 280, and aplasma 299 formed therein, are also shown. FIG. 7 shows the cutawaytaken through one of metal sections 245. Some outlet apertures 270 aredefined by dielectric break 240 on axial side 211(2) of plasma block210(3), as shown. Plasma cavity 280, and plasma 299 formed therein, arealso shown.

FIGS. 6 and 7 also show cooling tubes 275 through magnetic elements220(3). Cooling tubes 275 may provide fluid connections for gases orliquids to remove heat dissipated by magnetic elements 220(3); thefeature of providing cooling channels is contemplated for any of themagnetic elements described herein, although not shown in many cases forclarity of illustration. Similarly, cooling tubes may be provided ininduction coils 230 and/or various other plasma source components; somesuch arrangements are shown and described herein while others are not,for clarity of illustration.

FIG. 8 schematically illustrates a portion of a direct outlet toroidalplasma source 600 in which a plasma cavity 280 is defined by disposing aplasma block 210(4) adjacent a plate 610. A direction 10 of the toroidalaxis, and radial direction 2 are shown again in FIG. 8 for reference.The actual toroidal axis passes through a centroid of plasma cavity 280,outside the view of FIG. 8; an azimuthal direction arcs in and out ofthe plane of FIG. 8. For manufacturability and maintenance purposes, itmay be advantageous to provide a plasma cavity defined by componentsthat are easily machinable and interchangeable. Plasma source 600 thusdefines plasma cavity 280 by providing plasma block 210(4) as arelatively simple shape, with the ability to seal plasma block 210(4) toplate 610 that defines outlet apertures 270 therein. The ability to sealplasma block 210(4) to plate 610 is provided by grooves 615 in plate 610that accommodate one or more o-rings 620. When plasma cavity 280 isevacuated, external atmospheric pressure forces plasma block 210(4)against o-rings 620 to form the seal. In the embodiment shown in FIG. 8,plate 610 is formed of a dielectric material. Suitable materials forplate 610, as well as dielectric breaks 240, include ceramics, inparticular aluminum nitride or aluminum oxide, or fused quartz. Formingplate 610 of a dielectric material allows dielectric breaks 240 ofplasma block 210(4) to interrupt azimuthal currents so that plasma 299can form; that is, if plate 610 were formed of metal and wereelectrically coupled to plasma block 210(4), electric currents inducedby the magnetic elements would merely race around the azimuthal circuitthus formed, reducing the coupling of electric fields into plasma cavity280. Dielectric breaks 240 extend completely around the minorcircumference of plasma blocks 210 herein; in the azimuthal direction,dielectric breaks 240 need to be of sufficient width to inhibitelectrical arcing of adjacent metal segments of the plasma block 210,such as about one quarter inch to one inch.

FIG. 9 schematically illustrates a direct outlet toroidal plasma source700 having a plasma cavity 280 that is defined by disposing a plasmablock 210(5) adjacent a plate 710. Direction 10 of the toroidal axis,and radial direction 2, are shown again in FIG. 9 for reference;azimuthal direction arcs in and out of the plane of FIG. 9. Plate 710 isformed of a conductor, and includes a dielectric barrier 720 at asurface thereof that contacts plasma block 210(5). Dielectric barrier720 thus defeats shorting of plasma block 210(5) to the conductorforming plate 710, to interrupt the azimuthal currents that wouldotherwise form. Plasma source 700 thus defines plasma cavity 280 byproviding plasma block 210(5) as a relatively simple shape, with theability to seal plasma block 210(5) to plate 710 that defines outletapertures 270 therein. The ability to seal plasma block 210(4) to plate710 is provided by grooves 715 in plasma block 210(5) that accommodateone or more o-rings 620. When plasma cavity 280 is evacuated, externalatmospheric pressure forces plate 710 against o-rings 620 to form theseal. The design illustrated in FIG. 9 enables plasma block 210(5) andplate 710 to be held at different potentials; this allows control of aratio of radicals to ions within plasma products emitted through outputapertures 270 toward a processing location. FIG. 9 also shows coolingtubes 775 that provide gas or liquid cooling of plate 710. Cooling tubes775 may be provided in other components herein, such as plasma blocks,top or bottom plates of plasma sources or plasma chambers, or side wallsof plasma chambers.

FIG. 10 schematically illustrates a direct outlet toroidal plasma source800, showing an inlet gas manifold 810 that supplies source gases to aplasma cavity therein. Radial direction 2 and azimuthal direction 3 areshown in FIG. 10 for reference; the toroidal axis 1 extends out of theplane of FIG. 10. The top view illustrated in FIG. 10 shows magneticelements 220(3) on opposing sides of a plasma block 210(6), with a pairof gas manifolds 810 on either side. Each of gas manifolds 810 receivessource gases through one or more inlets 820; although only one inlet 820is illustrated in FIG. 10, it is understood that inlets 820 may vary innumber and position. Gas manifold 810 distributes the source gases intoplasma block 210(6) through apertures therein, as now discussed. Abroken line 11-11 indicates a cross-sectional plane of plasma source 800that is illustrated in further detail in FIG. 11.

FIG. 11 is a schematic cutaway view along broken line 11-11 of FIG. 10,illustrating direct outlet toroidal plasma source 800. The toroidal axis1 and radial direction 2 are shown again in FIG. 11 for reference;azimuthal direction arcs in or out of the plane of FIG. 11, changingsign from left to right of toroidal axis 1. An inlet gas stream isintroduced into gas manifolds 810 through inlet apertures 820, thenpasses into plasma cavity 280 through apertures 830 defined by plasmablock 210(6). Inlet apertures 820 are shown as vertical (e.g., parallelwith toroidal axis 1) in the view of FIG. 11, but may be defined atother angles to encourage mixing or other effects in plasma cavity 280(see also FIGS. 12 and 13). Gas manifold 810 may be constructed tocontain only a small gas volume so that changes in the source gas stream(e.g., introduced by upstream valves or other gas management equipment)rapidly transfer into plasma cavity 280. Gas manifold 810 may include apressure sensor to provide information about pressure therein, tofacilitate understanding of factors affecting plasma processing.Material choices for a gas manifold 810 are the same as for a plasmablock 210 that it is associated with; for example metals such asaluminum, with or without treated surfaces, or dielectrics such asalumina, aluminum nitride, and other ceramics are possible choices. Whengas manifold 810 and its associated plasma block 210 are both made ofmetal, it may be desirable to isolate gas manifold 810 from plasma block210 and/or to provide dielectric breaks in gas manifold 810, to avoidcompleting an azimuthal electrical circuit, as discussed above.

FIG. 12 schematically illustrates a plasma block 210(7) of a directoutlet toroidal plasma source with an inline gas inlet aperture 850 forintroducing source gases. The toroidal axis 1, radial direction 2 andazimuthal direction 3 are shown again in FIG. 12 for reference. Inlinegas inlet aperture 850 is substantially azimuthally aligned with plasmacavity 280, as shown. Introducing a source gas stream through gas inletaperture 850 imparts an azimuthal velocity to the injected gas toencourage thorough mixing within plasma block 210(7). In embodiments,inline gas inlet aperture 850 may be exactly azimuthally aligned, asshown in FIG. 12, however in other embodiments an inline gas inletaperture may be only partially aligned, for example defining an anglewhere it intersects plasma cavity 280. A source gas passing through aninline gas inlet aperture 850 at any angle having a nonzero azimuthalcomponent relative to the toroidal axis will generate at least someazimuthal velocity in the gas as it is introduced into plasma cavity280.

FIG. 13 schematically illustrates a plasma block 210(8) of a directoutlet toroidal plasma source with a plurality of inline gas inletapertures 850. The toroidal axis 1, radial direction 2 and azimuthaldirection 3 are shown again in FIG. 13 for reference. It is contemplatedthat any number of inline gas inlet apertures 850 could be utilized, andthat inline gas inlet apertures 850 could be used in combination withgas inlet apertures at other angles and/or with variations of gasmanifold 810, as illustrated in FIGS. 10 and 11.

FIG. 14 schematically illustrates a plasma block 210(9) of a directoutlet toroidal plasma source 900, showing how outlet apertures 270 maybe defined at a plurality of angles 920 with respect to a surface normalof a plate 910 that forms one axial side thereof. Direction 10 of thetoroidal axis, and radial direction 2, are shown again in FIG. 14 forreference; azimuthal direction arcs in and out of the plane of FIG. 14.Forming outlet apertures 270 at a plurality of angles can help indistributing plasma products broadly into an adjacent plasma processingapparatus, to facilitate uniform processing.

FIG. 15A is a schematic bottom view illustration of a direct outlettoroidal plasma source 1000 in which four outlet apertures 270 aredefined. The view of FIG. 15 schematically depicts a bottom plate ofdirect outlet toroidal plasma source 1000, with approximate boundariesof a plasma block on the other side of the plate suggested by brokenlines. Even with only four outlet apertures 270, plasma source 1000 mayprovide significantly more uniform processing than prior art remoteplasma sources that extract output from only one aperture. Toroidal axis1 extends into the planes of FIGS. 15A and 15B; radial direction 2 andazimuthal direction 3 are shown in FIG. 15A for reference but areomitted in FIG. 15B for clarity of illustration. FIG. 15B is a schematicbottom view illustration of a direct outlet toroidal plasma source 1100in which over sixty outlet apertures 270 are defined. The view of FIG.15B schematically depicts a bottom plate of direct outlet toroidalplasma source 1100, with approximate boundaries of a plasma block on theother side of the plate suggested by broken lines. Geometries andmaterials of the corresponding plasma block, number and placement ofmagnetic elements and induction coils may be optimized to generate auniform plasma distribution within the plasma block such that plasmaproducts extracted through outlet apertures 270 are spatially uniformacross plasma source 1100. In embodiments, a direct toroidal plasmasource may include hundreds or thousands of outlet apertures 270.

FIG. 16 schematically illustrates, in a cross-sectional view, a plasmawafer processing system 1200 that includes two direct outlet toroidalplasma sources 1201 and 1202. Only representative components ofprocessing system 1200 are labeled, and FIG. 16 is not drawn to scale,for clarity of illustration. The toroidal axis 1 and radial direction 2are shown again in FIG. 16 for reference; azimuthal direction arcs in orout of the planes of FIG. 16, changing sign from left to right oftoroidal axis 1. Plasma wafer processing system defines a processchamber 1234 that is radially symmetric about toroidal axis 1; thusplasma source 1201 may be considered an outer plasma source while plasmasource 1202 may be considered an inner plasma source, with the toroidalaxes of plasma sources 1201 and 1202, and an axis of symmetry of plasmachamber 1234, all being coincident. Again, although FIG. 16 is anembodiment directed to wafer processing, it is understood that otherembodiments may utilize the same principles for processing of otherworkpieces.

Plasma wafer processing system 1200 utilizes plasma sources 1201 and1202 to generate plasma products, and is configured for optional mixingof the plasma products with un-activated gases as they move from thelocation of the plasma to a workpiece 50 being processed. Plasma waferprocessing system 1200 defines a process chamber 1234 in which apedestal 1235 positions a workpiece 50 at a processing location, asshown. Plasma source 1201 forms an outer toroidal shape, and plasmasource 1202 forms an inner toroidal shape, atop a top surface 1232 ofchamber 1234. Plasma sources 1201 and 1202 may receive source gases frominlet apertures 260 or 830, as shown in FIGS. 5 and 11 respectively,with or without a gas manifold 810 as shown in FIGS. 10 and 11; suchstructures are not shown in the view of FIG. 16. Each of plasma sources1201 and 1202 includes a respective plasma block 210(10) or 210(11), andutilizes induction coils 230 and magnetic elements 220(3) to generate aplasma from the source gases therein. Plasma sources 1201 and 1202 sharea common bottom plate 1210 that defines apertures 270 for distributingplasma products toward process chamber 1234.

Apertures 270 in the bottom plate 1210 provide uniform, axial direction(e.g., in the direction of the toroidal axis) and short paths for plasmaproducts to be distributed from the plasma where they originate, toworkpiece 50 being processed. The use of two plasma sources 1201 and1202, with plasma source 1201 defining an outer toroid and plasma source1202 defining an inner toroid, provides a significant degree of freedomin optimizing center-to-edge uniformity of processing for workpiece 50.Process recipes may be optimized by varying process parametersparticular to plasma sources 1201 and 1202 and measuring effects on testand/or product wafers processed in system 1200. Overall gas flows and RFenergy provided to plasma sources 1201 and/or 1202 may be adjusted untilthe effects are uniform across each workpiece 50 processed. Inembodiments, plasma sources 1201 and 1202 may run different ratios ofreactive gases than one another, and/or may utilize entirely differentsource gases than one another.

Processing system 1200 also provides gas inlets 1270 that pass throughbottom plate 1210 and top surface 1232, for supplying un-activated gasesto be mixed with the plasma products (see also FIG. 17A). The number anddistribution of apertures 270 and/or gas inlets 1270 shown in FIGS. 16and 17A are representative only, and may vary among embodiments.

Bottom plate 1210 is separate from top surface 1232 of chamber 1234 inembodiments, as shown, for ease of assembly and interchangeability ofparts. That is, plasma sources 1201 and 1202 may be assembled withbottom plate 1210 and installed or removed from top surface 1232 as asingle unit. However, in embodiments, the features of bottom plate 1210and top surface 1232 may be combined in a single plate.

FIG. 16 also shows an optional diffuser plate 1237 that definesapertures 1247 for the plasma products to proceed into process chamber1234. Diffuser plate 1237 can also include one or more gas passages 1239to conduct un-activated gases that can mix with the plasma products. Forexample, as shown in FIG. 16, gas passage 1239 connects with output gasapertures 1241 defined in a chamber-facing side of diffuser plate 1237(see also FIG. 17B). The number and distribution of apertures 1247and/or output gas apertures 1241 shown in FIGS. 16 and 17B arerepresentative only, and may vary among embodiments.

FIG. 17A schematically illustrates an upward facing, schematic plan viewof top surface 1232 of plasma processing system 1200, FIG. 16, withfeatures of bottom plate 1210 of direct toroidal plasma sources 1201 and1202 visible. Only representative components of top surface 1232 andbottom plate 1210 are labeled, and FIG. 17A is not drawn to scale, forclarity of illustration. The toroidal axis, radial and azimuthaldirections are not shown in FIGS. 17A and 17B, but can be determinedfrom those shown in other drawings. The numerous apertures 270 providepaths for plasma products from plasma sources 1201 and 1202 that arevery short and uniform in length, from the plasmas where they aregenerated, to the workpiece being processed, promoting uniformprocessing across chamber 1234. For example, paths from plasma withinplasma sources 1201 and/or 1202, to any location on workpiece 50, may beless than four inches, in embodiments. Providing gas inlets 1270interspersed with apertures 270 enables mixing un-activated gases withthe plasma products. Certain embodiments advantageously process waferswith plasma products and un-activated gases as they emerge from thestructures shown in FIG. 17A, that is, in processing systems 1200 thatdo not include diffuser 1237. Other embodiments may benefit from theadditional gas and plasma product mixing provided by diffuser plate1237.

FIG. 17B schematically illustrates an upward facing, schematic plan viewof diffuser 1237. Only representative features of diffuser plate 1237are labeled, and FIG. 17B is not drawn to scale, for clarity ofillustration. Apertures 1247 (illustrated as open circles) extend allthe way through diffuser plate 1237, while outlet gas apertures 1241(illustrated as dots) extend only into the bottom surface of diffuserplate 1237, where they are supplied with un-activated gas from gaspassage 1239. Diffuser 1237 facilitates further mixing and fine controlof ratios of plasma products to un-activated gases, which may beadvantageous for some plasma processes, but may be unnecessary forothers.

FIG. 18 schematically illustrates, in a cross-sectional view, a plasmawafer processing system 1300 that includes two direct outlet toroidalplasma sources 1301 and 1302. Again, although FIG. 18 is an embodimentdirected to wafer processing, it is understood that other embodimentsmay utilize the same principles for processing of other workpieces. Manyfeatures of processing system 1300 will be recognized as substantiallysimilar to systems previously described and are not described again. Thetoroidal axis 1 and radial direction 2 are shown again in FIG. 18 forreference; azimuthal direction arcs in or out of the planes of FIG. 18,changing sign from left to right of toroidal axis 1. Plasma waferprocessing system defines a process chamber 1334 that is radiallysymmetric about toroidal axis 1; thus plasma source 1301 may beconsidered an outer plasma source while plasma source 1302 may beconsidered an inner plasma source, with the toroidal axes of plasmasources 1301 and 1302, and an axis of symmetry of plasma chamber 1334,all being coincident. FIG. 18 illustrates the additional feature ofplasma blocks 210(12) and 210(13) that are in open fluid communicationwith underlying spaces, rather than being bounded by bottom plates. FIG.18 also illustrates a domain separator 1360.

Similar to the respective locations of plasma sources 1201 and 1202,plasma sources 1301 and 1302 define inner and outer toroidal shapes atopa process chamber 1334. Plasma sources 1301 and 1302 may receive sourcegases from inlet apertures 260 or 830, as shown in FIGS. 5 and 11respectively, with or without a gas manifold 810 as shown in FIGS. 10and 11; such structures are not shown in the view of FIG. 18. Withinprocess chamber 1334, a pedestal 1335 positions workpiece 50 forprocessing. Plasma blocks 210(12) and/or 210(13) form substantiallyazimuthally continuous openings 1370 on a first axial side thereof, thatis, plasma sources 1301 and 1302 are not substantially bounded on thefirst axial side, as are plasma sources 1201, 1202 and others previouslydiscussed. Openings 1370 may be substantially azimuthally continuous inthat they extend significantly in the azimuthal direction through topplate 1332, however, in this context “substantially azimuthallycontinuous” does not preclude interruptions to openings 1370 to providemechanical support for radially inner portions of top plate 1332;openings corresponding to at least about 75% of the major circumferenceof either plasma source would be considered substantially azimuthallycontinuous. Also, it is not critical that both plasma blocks 210(12) and210(13) define substantially azimuthally continuous openings; inembodiments, one of plasma blocks 210(12) and 210(13) defines asubstantially azimuthally continuous opening while the other does not.Thus, plasma cavities of plasma sources 1301 and 1302 are in fluidcommunication with spaces 1355, 1357 formed in an upper portion ofprocess chamber 1334, such that plasma products will pass out of plasmablocks 210(12) and 210(13) through openings 1370 into spaces 1355 and1357. From spaces 1355, 1357 the plasma products pass through a diffuserplate 1337 into process chamber 1334.

Plasma wafer processing system 1300 may, of course, include provisionsfor supplying source gases to plasma sources 1301 and 1302 (such asindividual gas inlet apertures and/or gas manifolds as described inconnection with FIGS. 10-13) and for adding further gases to the plasmaproducts, such as gas inlets 1270 and/or gas passages 1239 illustratedin FIGS. 16, 17A and 17B.

The open design of plasma blocks 210(12) and 210(13) means that pressurein each of spaces 1355, 1357 beneath each plasma block will besubstantially determined by input gas flow to the respective plasmablocks. Separation of spaces 1355 and 1357 can thus be maintained, ifdesired, by using a domain separator 1360. Domain separator 1360 is acircular feature that contacts both top plate 1332 and diffuser plate1337 about its complete circumference; the cross-sectional view of FIG.18 shows only two portions of domain separator 1360 that pass throughthe cross-sectional plane. Domain separator 1360 is typically formed ofdielectric material and enforces a separation between plasma productssupplied to a center region and an edge region of process chamber 1334.This separation can be used, in embodiments, to control center and edgeprocessing effects separately within process chamber 1334, and thus tooptimize center-to-edge processing uniformity at workpiece 50.

The provisions for supplying source gases to plasma sources 1301 and1302 may be independently controllable so that process effects at acenter region and an edge region of the process chamber (e.g.,corresponding approximately to those regions most influenced by plasmasources 1302 and 1301 respectively) can be adjusted for best processinguniformity. Independent controllability of source gases to plasmasources 1301 and 1302 may be advantageous whether or not domainseparator 1360 is present.

From the preceding descriptions, it should be clear that one, two ormore toroidal plasma sources may be utilized to provide uniformdistributions of plasma products to a process chamber, by extracting theplasma products from axial sides of the plasma sources along shorttravel paths to the process chamber. A plurality of toroidal plasmasources may be disposed with elements such as respective plasma blocks,dielectric breaks of the plasma blocks, magnetic elements, inductioncoils, cooling apparatus, output apertures, inlet gas manifolds andother associated elements arranged for best uniformity and shortesttravel paths of plasma products to the process chamber.

Having described several embodiments, it will be recognized by those ofskill in the art that various modifications, alternative constructions,and equivalents may be used without departing from the spirit of theinvention. Additionally, a number of well-known processes and elementshave not been described in order to avoid unnecessarily obscuring thepresent invention. Accordingly, the above description should not betaken as limiting the scope of the invention.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimits of that range is also specifically disclosed. Each smaller rangebetween any stated value or intervening value in a stated range and anyother stated or intervening value in that stated range is encompassed.The upper and lower limits of these smaller ranges may independently beincluded or excluded in the range, and each range where either, neitheror both limits are included in the smaller ranges is also encompassedwithin the invention, subject to any specifically excluded limit in thestated range. Where the stated range includes one or both of the limits,ranges excluding either or both of those included limits are alsoincluded.

As used herein and in the appended claims, the singular forms “a”, “an”,and “the” include plural referents unless the context clearly dictatesotherwise. Thus, for example, reference to “a process” includes aplurality of such processes and reference to “the electrode” includesreference to one or more electrodes and equivalents thereof known tothose skilled in the art, and so forth. Also, the words “comprise,”“comprising,” “include,” “including,” and “includes” when used in thisspecification and in the following claims are intended to specify thepresence of stated features, integers, components, or steps, but they donot preclude the presence or addition of one or more other features,integers, components, steps, acts, or groups.

We claim:
 1. An apparatus for supplying plasma products, comprising: aplasma generation block that defines a toroidal plasma cavity therein, ashape of the plasma cavity being substantially symmetric about atoroidal axis, the toroidal axis defining a first and second axial sideof the plasma generation block; and a magnetic element that at leastpartially surrounds the plasma generation block at one azimuthallocation with respect to the toroidal axis, such that a magnetic fluxwithin the magnetic element induces a corresponding electric field intothe plasma cavity to generate a plasma from one or more source gases,the plasma forming plasma products; wherein the plasma generation blocksupplies the plasma products through a plurality of output aperturesdefined by the plasma generation block on the first axial side.
 2. Theapparatus for supplying plasma products of claim 1, wherein the plasmageneration block defines at least four apertures as the plurality ofapertures, the four apertures being azimuthally spaced at approximatelyninety degree intervals.
 3. The apparatus for supplying plasma productsof claim 1, wherein the plasma generation block defines at least onehundred apertures as the plurality of apertures.
 4. The apparatus forsupplying plasma products of claim 1, wherein the plasma generationblock defines at least one thousand apertures as the plurality ofapertures.
 5. The apparatus for supplying plasma products of claim 1,wherein the plurality of output apertures define a plurality of angleswith respect to the toroidal axis.
 6. The apparatus for supplying plasmaproducts of claim 1, wherein the plasma generation block defines one ormore inlet apertures for supplying the one or more source gases to theplasma cavity.
 7. The apparatus for supplying plasma products of claim6, further comprising an inlet gas manifold disposed adjacent to thesecond axial side of the plasma generation block, the one or more inletapertures comprising a plurality of apertures defined by the plasmageneration block on the second axial side, for supplying the one or moresource gases from the inlet gas manifold to the plasma cavity.
 8. Theapparatus for supplying plasma products of claim 1, wherein at least oneof the one or more inlet apertures defines a nonzero azimuthal anglerelative to the toroidal axis.
 9. The apparatus for supplying plasmaproducts of claim 1, wherein the plasma generation block comprisesaluminum.
 10. The apparatus for supplying plasma products of claim 9,wherein the plasma generation block comprises at least one dielectricbreak that interrupts azimuthal current induced by the electric field.11. The apparatus for supplying plasma products of claim 10, wherein thedielectric break comprises a plurality of dielectric breaks that aresubstantially symmetrically distributed azimuthally about the plasmageneration block.
 12. The apparatus for supplying plasma products ofclaim 1, wherein the plasma generation block includes: a first memberthat bounds the plasma generation cavity on radially inward, radiallyoutward, and second axial sides thereof; and a plate on the first axialside that contacts the first member on radially inward and radiallyoutward edges thereof, the plurality of output apertures being definedby the plate.
 13. The apparatus for supplying plasma products of claim1, wherein the plasma generation block includes: a first memberincluding a radially inward surface, a radially outward surface, and anaxial surface that bound the plasma cavity on a second axial side; and aplate on the first axial side that contacts the radially inward andradially outward surfaces on edges thereof, the plurality of aperturesbeing defined through the plate.
 14. The apparatus for supplying plasmaproducts of claim 1, the inlet gas manifold supplying the one or moresource gases through a plurality of ports on a second axial side of theplasma generation cavity.
 15. The apparatus for supplying plasmaproducts of claim 1, the inlet gas manifold supplying the one or moresource gases through one or more ports that inject the one or moresource gases into the plasma generation cavity at an angle thatsubstantially tangent to a central axis of the plasma generation cavity.16. An apparatus for supplying plasma products, comprising: a plasmageneration vessel that defines a plasma cavity, the plasma cavity beingsubstantially symmetric about a toroidal axis, the plasma generationvessel comprising: a plasma generation block that bounds the plasmacavity on radially inward, radially outward, and second axial sidesthereof, and defines one or more apertures for introducing one or moresource gases into the plasma cavity, a planar plate disposed on a firstaxial side of the plasma cavity, the planar plate defining a pluralityof apertures therethrough that are azimuthally distributed about theplasma cavity, wherein radially inward and radially outward edges of theplasma generation block abut the planar plate to form the plasmageneration vessel, substantially enclosing the plasma cavity; first andsecond induction coils; a power supply for providing currents within thefirst and second induction coils; and first and second magnetic elementsextending at least partially about the plasma generation block anddisposed proximate the first and second induction coils respectively, sothat the currents induce magnetic fluxes within the magnetic elements,and the magnetic fluxes within the magnetic elements produce azimuthalelectric fields within the plasma cavity to form a plasma from the oneor more source gases, forming plasma products; such that the aperturesthrough the planar plate provide fluid communication for the plasmaproducts to an adjacent region for use in plasma processing.
 17. Amethod of providing plasma products, comprising: introducing a sourcegas stream into a plasma generation block that defines a toroidal plasmacavity therein, the plasma cavity being substantially symmetric about atoroidal axis, the plasma generation block defining a plurality ofoutput apertures only on a first axial side thereof relative to thetoroidal axis, the output apertures being substantially azimuthallydistributed about the plasma generation block; inducing an electricfield into the plasma cavity to generate a plasma from the source gasstream, the plasma forming the plasma products; and passing the plasmaproducts through the plurality of output apertures defined by the plasmageneration block.